As one of the conventional radio communication apparatus of this type, a radio telephone device A is shown in FIG. 8. The radio telephone device A is provided with a telephone set main body B as a mobile unit and a car kit C as an adapter.
The telephone set main body B is provided with a radio section (not shown) within its casing and a rod antenna Ba (a first antenna) extending outwardly which is used when the telephone set main body B is used as a portable telephone set.
The car kit C is fixed in a car and connected through an external cable D to an external antenna E (a second antenna). When the telephone set main body B is attached to the car kit C and connected with a connector cord Ca, the radio section (not shown) in the telephone set main body B and the external antenna E are connected to each other, whereby the telephone set main body B is used as a car-mounted telephone set with the use of the external antenna E.
As shown in parts (a) and (b) of FIG. 9, in the radio telephone device A, a high frequency relay R is used to switch an antenna line between the rod antenna Ba and the external antenna E.
The high frequency relay R is disposed within the casing of the telephone set main body B. Terminals a and b of the relay R are connected to a radio section F and the rod antenna Ba, respectively. When the telephone set main body B is disconnected from the car kit C, the terminals a and b are connected to each other through a movable spring contact Ra, whereby the radio section F is connected through the high frequency relay R to the rod antenna Ba so that telephonic communication is made through the rod antenna Ba.
When the telephone set main body B is attached to the car kit C and connected with the connector cord Ca, the external antennal E is connected to a terminal c of the relay R, as shown in the part (b) of FIG. 9. Supply of an electric current between coil terminals d and e of the relay R generates a magnetic field in a coil Rb which causes a movable spring contact Ra to be pulled downward, and the terminals a and c are connected to each other by the contact Ra. As a result, the radio section F is connected through the relay R to the external antenna E and telephonic communication is made through the antenna E.
In the conventional radio telephone device A, since the relay R is used to switch the antenna line between the rod antenna Ba and the external antenna E, as mentioned above, an electric current is required to be supplied through the coil Rb of the relay R when the antenna is switched and hence power consumption would increase disadvantageously.
In the conventional radio telephone device A, control means is required for detecting, when the telephone set main body B or connection of the external antenna E to the terminal c of the relay R so as to switchover the antenna line from the rod antenna Ba to the external antenna E and for supplying a current between the coil terminals d and e of the relay R. This would cause the circuitry to be complicated, disadvantageously.